9
Installation and Operating Manual
IP277, Rev DA
Mobrey MCU200 Series
February 2020
Ultrasonic gap sensor connections
The sensor connections on the PCB are labelled “1”, “E” for the receiver crystal and “E”, “2” for
the coax cable to the transmitter crystal. The screens of these coax cables must be connected to
the terminals marked “E”.
Auxiliary Input connection
The Auxiliary Input is a terminal which can be connected to a “push- to-reset” button to achieve
a latching alarm, or connected to another Mobrey control unit for pump control from the
MCU200 relay output.
If a short-circuit is connected between terminals 3 and 4, the MCU200 relay, when
de-energised, is held de-energised. Even if the sensor attached to the MCU200 changes state, to
that which should energise the output relay, this relay will not energise until the link between
terminals 3 and 4 is broken in the circuit external to the MCU200.
3.4
Internal switch settings
Gain switch (and potentiometer)
See
“Applications” on page 11
.
Frequency selection
This slide-switch is labelled “FREQ” and is located between the sensor terminal block “E 2”, and
the “Aux. Input” terminals. This switch selects the operating frequency of the MCU200
oscillator, which is either 3.7 MHz (switch in the 'up' position) or 1 MHz, (switch in the ‘down’
position).
The setting required is dependent on the sensor type connected to the control unit.
Usually these are:
Mobrey sludge sensors type 433 and 448 with the suffix M1, built after S/No 9001, can operate
at both 1 MHz and 3.7 MHz. The MCU201 selection switch determines the operating frequency.
Note
Where any sensor is built to operate at non-standard frequency, it will have the suffix M1 or M3
at the end of the type number.
Cable check option selection
This single slide-switch is labelled “Cable Check” and is located directly above the sensor
terminal block “E 2”. The ex-factory setting is “OUT” i.e. with the slide-switch to the right.
By sliding this switch to the left, the cable-check circuitry is enabled. This circuitry monitors the
continuity of the screens of the two coaxial cables attached to the sensors. Normally, these
cable screens are connected at the sensor-end to the metal body of a fitting (or to each other in
3.7 MHz sensors
40*S, 43*S, 44*S
